Aerodynamic separation of gas constituents is useful for a number of industrial and commercial applications. An aerodynamic separation nozzle, or, as used herein, a separation nozzle, uses aerodynamic effects and forces generated by high speed flow through structures to apply large centrifugal and aerodynamic forces to gases flowing through those structures to urge the various gas species that comprise a separation gas to be separated (i.e. process gas) apart thereby enabling separation of the gas species. The combination of the centrifugal forces and the design of the structure are adapted to the type of gas species being separated. In particular, the invention disclosed herein in its various embodiments preferentially separates and isolates the constituents of a process gas into heavier and lighter species that are suitable for concentration and collection. In one aspect the aerodynamic separation nozzle utilizes temperature control of the nozzle to enhance separation efficiency. In another aspect, the aerodynamic separation nozzle utilizes pre-conditioning of the incoming gas stream to enhance separation efficiency. In still other aspects combinations of the foregoing are used to enhance separation efficiency.
1 Industrial Applicability
The system and method has potential applicability to a wide range of different industrial and commercial applications. The following brief synopsis is intended only to provide background on some exemplary applications to assist a person of ordinary skill in the art in understanding this disclosure more fully.
1.1 Natural Gas Processing
Natural gas provides more than one-fifth of all the primary energy used in the United States. Much of the raw natural gas is sub-quality and exceeds pipeline specifications for carbon dioxide, hydrogen sulfide, and nitrogen content, and much of this low-quality natural gas cannot be produced economically with present processing technology.
A number of industry trends are affecting the natural gas industry. Despite the current high price of natural gas, long-term demand is expected to overcome supply, requiring new gas fields to be developed, including gas fields not being used because of their low-quality products. In the future, the proportion of the gas supply that must be treated to remove contaminants before introduction into the pipelines will increase.
Amine gas treating, or acid gas removal, refers to a group of processes that use aqueous solutions of various amines to remove carbon dioxide (CO2) and hydrogen sulfide (H2S) from gases. It is a common unit process used in refineries, petrochemical plants, gas-processing plants, and gasification plants. Gases containing carbon dioxide and/or hydrogen sulfide are commonly referred to as acid gases or sour gases in the hydrocarbon processing industries.
A typical amine gas treating process includes an absorber unit and a regenerator unit in addition to other ancillary equipment. In the absorber unit, the down-flowing amine solution absorbs CO2 and H2S from the up-flowing sour natural gas to produce a gas that meets specifications for CO2 and H2S content that exits the absorber unit. The resultant ‘rich’ amine is then routed into a regenerator (a stripper with a reboiler) to produce regenerated or ‘lean’ amine that is recycled for reuse in the absorber.
A similar process is used in the steam reforming process of hydrocarbons to produce gaseous hydrogen for subsequent use in the industrial synthesis of ammonia. Amine treating is one of the commonly used processes for removing excess carbon dioxide in the final purification of the gaseous hydrogen.
Problems associated with amine treating include the energy expense of the process, the chemical expense of the process (due to evaporative loss of amine), the inability to process highly contaminated CO2 gases, and the emission of gases during the regeneration stage to the atmosphere.
As of 2005, according to the EPA there are 287 acid gas removal (“AGR”) units operating in the natural gas industry in the United States. These AGR units collectively emit 634 million cubic feet (MMcf) of methane to the atmosphere annually, averaging 6 thousand cubic feet per day (Mcf/day) of methane per individual AGR unit. Methane is a known greenhouse gas, collectively less in quantity in the atmosphere when compared to carbon dioxide, but having about 20 times the heat insulation properties than carbon dioxide, and has a life-span in the atmosphere of 12 years on average.
One need in industry today and for the future, is an acid-gas removal technology that can process high-levels of contaminants efficiently and does not require chemicals for absorption, and does not emit contaminants to the atmosphere. The present system and method is capable of separating CO2 and H2S from a sour natural gas stream without the need to use an amine based process thereby eliminating the need for costly, polluting AGR units.
1.2 Carbon Dioxide Capture
Extensive efforts have recently been directed toward capturing CO2 emitted from large point sources such as fossil fuel power plants and other fossil fuel powered thermal generation units. There are a number of processes that have been posited for commercial use at large point sources of CO2 including the same amine process described above for removing CO2 from sour natural gas. However, the same limitations caused by the operation of AGR units are present when using the process to capture carbon being emitted from a large point source. Further, additional technologies such as scrubbers, electrostatic precipitators and flue gas de-sulfurization is needed to remove sulfur dioxide (SO2) and particulate matter from the flue gas. In the case of large point source emitters, a separation nozzle can be employed to remove all of the contaminants in the exhaust stream, thereby allowing the concentration of the various gases and particulates in separate streams for final processing and in the case of carbon capture plants, sequestration of the CO2.
1.3 Oxygen Concentration
Many persons having diminished lung capacity need to breath either pure or enriched oxygen as part of their therapy. Traditionally, when persons need continuous oxygen therapy, they use an oxygen concentrator that use typically a molecular sieve, such as a zeolite, to remove nitrogen from ambient air, thereby concentrating oxygen for use in the therapy. These oxygen concentrators are typically less expensive than liquid oxygen canisters, and thus are more commonly used for home administration of oxygen therapy. However, oxygen concentrators capable of supplying more than 1-2 liters per minute of oxygen are typically larger, bulkier units that are not suitable for portable use and require large quantities of energy to operate. Thus, most patients who require oxygen therapy when outside the home must use traditional liquid oxygen bottles that are heavy and potentially dangerous. The present separation nozzle can provide the performance of an oxygen concentrator by separating ambient air into its constituent gases, thus concentrating the oxygen present in ambient air to a level suitable for oxygen therapy, without the need for bulky, power-intensive molecular sieves.